The present invention relates to hydraulic lash adjusters and more particularly to a hydraulic lash adjuster adapted to be used in the valve train of an internal combustion engine.
In the valve trains of internal combustion engines, predetermined valve clearances are generally provided in order to compensate for thermal expansion of various parts in the valve trains. However, since excessive lash may be generated due to valve clearances in the valve trains during engine operation, hydraulic lash adjusters have been used for automatically taking up the valve clearances in valve trains to thereby prevent undesirable noises.
Conventional lash adjusters include a plunger slidably arranged within a body to define a reservoir chamber therein, a pressure chamber to which a pressure receiving surface of the plunger is exposed and a check valve which will allow the flow of a fluid, such as oil, from the reservoir chamber to the pressure chamber. The reservoir chamber receives the fluid from an external source outside the body by means of a port provided in the plunger and a supply port provided in the body. In order to ensure the transmission of fluid from outside of the body to the reservoir chamber without undesirable problems regarding alignment of the ports, the body is usually provided with annular grooves 142 and 42' as shown in the prior art example of FIG. 4 which face the plunger and the engine block, respectively, and which are in communication with the supply port 44' extending through the body. However, the body must have a predetermined thickness throughout its entire length, even at the portion thereof at which the annular grooves 142 and 42' are located in order to provide sufficient strength for the body. In other words, the thickness of the remaining portions of the body must be unnecessarily increased in order to provide sufficient thickness in the vicinity of the grooves and therefore the weight of the body is substantially increased. Since the body undergoes vigorous reciprocating motion it is undesirable to have such an increase in the weight of the body.